Load transference unit



@9 2%, Ji. H. www mm2@ LOAD TRANSFERENCE UNIT Filed Aug. 14, 1945Patented Aug. 6, `l 946 UNITED STATES PATENT GFFICE LOAD TRANSFERENCEUNIT J ames H. Jacobson, Chicago, Ill.

Application August 14, 1943, Serial No. 498,660

2 Claims.

The load transference unit of the present invention is designedprimarily for use in the construction of concrete highways, for thepurpose of connecting the ends of adjoining road slabs, and transmittingload stresses across the gaps between the adjacent faces of the slabs insuch a manner as to prevent vertical displacement under the pressure ofa rolling load on a highway, runway or the like.

Before discussing the mechanical details of the present invention it isproper to point out that the term load transference unit refers to themeans employed for interconnecting the adjacent ends of concrete roadslabs across the gap provided for expansion and contraction and whichunit includes members which are movable horizontally to accommodate theadvance and recession of the slabs, and which serve in conjunction witha dowel bar to bridge the gap and resist vertical displacement of eitherof the slabs'with respect to the other. In such an arrangement it is ofprimary importance to distribute the stresses imposed by an approachingload, so that a considerable portion of such stress will be resisted bythe more distant slab, which thus serves to reinforce the near slabwhich receives the initial impact of the advancing load, and it is alsoimportant to provide against vibration or similar movements which,unless counteracted, have a cumulative tendency to wear away theconcrete adjacent the unit members, and thus in time permit displacementof the unit with a resulting failure to perform the service intended. v

The load transference unit members which are especially adapted for usewith thin slabs, have been designed with a view to extreme economy inproduction, being in the preferred form of identical stampings, whichmay be cut from a bar of metal with little waste of material and bent tonished form, ready for use, by a stamping operation, and which need notbe cut or formed with extreme precision in order to be intertted in theintended manner for use in a road joint. It will be understood, however,that the present unit need not be formed as a stamping, but may beproduced as a malleable unit or otherwise.

Further objects and details will appear from the description of theinvention in conjunction with the accompanying drawing, wherein- Figure1 is a perspective view of identical companion unit members in theirassembled relation;

Fig. 2 is a face view of one of the unit members;

Fig. 3 is an edge View of the assembled unit embedded in the faces ofopposed concrete slabs on opposite sides of a road joint; and

Fig. 4 is a modification showing the provision of anchoring members.

Each unit member in the form shown is formed from plate material cut orstamped to afford a flat body portion I0 having spaced arms I Iextending upwardly therefrom to afford a gap I 2, the base of which isafforded by the middle edge section I3 of the body I0.

With the opposed unit members aligned as in Fig. 1, the edges I3 affordsupport for a at dowel bar I4, the middle portion of which bridges the'gap across the joint between the concrete slabs I5 of a road or similarstructure which present their at vertical faces I6 in opposed relationto one another.

Each of the unit members is provided with a rearwardly extending foot Ilstruck backwardly from one edge of the body portion to providesupporting contact with the surface of the subgrade, while the oppositeedge is extended downwardly in the form of a pointed spike I8 which isdriven into the subgrade as shown in Fig. 3.

The dowel bar is of a width to lie between the upstanding arms I I andis preferably, though not necessarily, secured to one of the unitmembers by a line of welding I9 and has sliding contact across the bodyof the companion member to allow for expansion and contraction of theconcrete due to thermal changes. The outer free end of the dowel bar isentered into a sheath 20 which is xedly embedded in the concrete andaffords clearance for the in and out sliding movements of the dowel bar.

When the unit members are embedded within the concrete slabs as in Fig.3, the faces of the opposed members will lie iiush with the verticalfaces of the slabs while the oppositely extending feet will be embeddedaround their top faces and edges with their under horizontally extendedfaces abutting flatwise with the subgrade.

While it will not ordinarily be necessary to provide additionalanchoring means for holding the unit members in place within theconcrete slabs, nevertheless in some cases such anchors may be desirableand in Fig. 4 I have shown upper middle and lower anchors 2|, 22, and 23which enter deeply into the body of concrete and assist in anchoring theunit members against displacement. The upper anchors are formed bystriking back the upper ends of the arms II while the lower anchor isformed by striking up the end of the foot I'I. The middle anchor isformed by striking back a tongue cut free from the arms I I.

One or more of such supplemental anchoring devices or others of similarcharacter may be em- 3 ployed without otherwise modifying the structureor mode of operation of the device.

In use properly spaced unit members are driven into the subgrade untilthe feet make contact with the surface and thus afford stops forensuring that companion members will stand at the same level so that thedowel bar, which is preferably connected with one of the members will ntproperly within the other.

The free end of the dowel bar will be capped with the sheath 20 whichextends beyond the end of the bar, so that space will be aiorded withinthe concrete for the free sliding movements of the bar. With the unitmembers thus staked in position, and the dowel bar in place and withsuitable forms or spacers employed to provide the intended gap betweenthe slabs, the concrete will be poured and compacted and built up to alevel above the tops of the arms H, and if anchoring wings or flanges ofthe; character shown in Fig. 4 are employed, the same will be embeddeddeeply within the body of the concrete.

The device is one which combines great strength through its resistanceto stresses, with tensile strength in resistance to shear. It may bereadily installed by simply driving-it into the earth to any desiredheight of dowel bar and still function correctly While the dowel baritself is held in place rigidly and at the same time is free to movehorizontally. Although the form shown is one which combines extremesimplicity with cheapness in production, it is obvious that changes inthe shape or proportions of the constituent parts may be made withoutdeparting from the spirit of the invention.

I claim:

l. In combination with concrete pavement slabs presenting opposed edgefaces on opposite sides of a gap, a load transference unit comprise ingoppositely facing unit members each formed of plate material adapted toafford great resistance to load stresses, and having a body and spaced,upwardly extending arms in the plane of thebody and presenting theirexposed faces ilush with the edge faces of said opposed concrete slabs,the body of each unit member being in part extended to provide adownwardly projecting spike entered into the subgrade and in partextended horizontally to provide a ilat faced foot underlying theconcrete and contacting the subgrade, a dowel bar bridging the spacebetween the slabs and the unit members and supported between the spacedarms, and rigidly secured to one of the unit members, and having itsends extended backwardly therefrom and into the respective slabs, oneend portion of the dowel bar having a slidable contact with the other ofsaid unit members, and a sheath loosely arranged on said dowel bar endportion and located beyond the adjacent unit member and positionable onthe dowel bar independently of said adjacent unit member.

2. In combination with concrete pavement slabs presenting opposed edgefaces on opposite sides of a gap, a load transference unit comprisingoppositely facing unit members each formed of plate material adapted toafford great resistance to load stresses, and having a body and spacedupwardly extending arms in the plane of the body and presenting theirexposed faces ilush with the edge faces of said opposed concrete slabs,the upper terminals of the arms being extended outward horizontally toprovide upper anchors and the body of each unit member being in partextended to provide a downwardly projecting spike entering into thesubgrade and in part extended horizontally to provide a flat faced footunderlying the concrete and contacting the subgrade, the terminal of thefoot being extended upwardly to provide a lower anchor, a middle anchorrigid with and extending outward horizontally from the body at the lowerend of the space between said arms, a at relatively broad dowel barpresenting its flat upper and lower faces in horizontal planes andrigidly secured to one of the unit members and bridging the spacebetween the unit members and supported between the spaced arms andhaving its ends extended backwardly therefrom into the respective slabs,one end portion of the dowel bar having a slidable contact with theother of said unit members, and a sheath loosely arranged on said dowelbar end portion and located beyond the adjacent unit member andpositionable on the dowel bar independently of said adjacent unitmember.

JAMES H. JACOBSON.

